Spatial patterns and temporal trends of trace metal mass budgets in the western Adriatic sediments (Mediterranean Sea)

Spatial patterns of major (Al, Fe and Ti) and trace metals (Cu, Cr, Mn, Ni, Pb and Zn) measured in surficial sediments collected within the Late-Holocene mud-wedge in the western Adriatic Sea were analyzed to elucidate their sources, transport and mass budgets. Distributions of sedimentary trace metals, their fluvial inputs and accumulation loads reveal along-shore transport towards the southern Adriatic. Pb and to a lower extent Zn accumulation loads over time decreased significantly since 1988 in the North Adriatic, consistently with the implementation of regulations in the Western Europe, whereas Zn accumulation in the Po River prodelta remained unchanged since 1995. The Po River fluvial inputs accounted for half of Cr, Ni, Pb and Zn of the fluvial inputs into the western Adriatic Sea, contributing for the delivery of important amounts of Cr and Ni into the sediments, probably related to the natural occurrence of ultramafic rocks in the North sector. Collectively, ~ 30% of trace metal fluvial inputs discharged into the North sector are exported to the Central and South sectors. The Po River acts as both a bypass and an accumulation zone. In contrast, trace metal accumulation in the Central sector far exceed trace metal fluvial inputs, which suggested that this area is a preferential sink for particle-reactive river-borne material from the North Adriatic. The North sector shows moderate enrichment of Zn and Pb mainly related to the Po River influence. The anthropogenic fraction of Pb shows a large drop of ~ 30% from the North sector southwards, whereas Zn proportions remain fairly the same up to the Central sector only decreasing in the South sector.